[Ur] Issues with automake 1.12

[Adam Chlipala]

Lance Hepler wrote:
> I propose one of the two following patches for configure.ac 
> <http://configure.ac/> and/or Makefile.am to deal with issues in 
> automake 1.12:
>
> Both patches add the AM_PROG_AR pragma which automake 1.12 seems to 
> require.
>
> The first patch just adds a -Wno-portability flag to AM_INIT_AUTOMAKE 
> to prevent "warning: ':='-style assignments are not portable" errors. 
> The latter actually just patches the uses of := in Makefile.am, 
> addressing the warnings presented. Not wanting to make stylistic 
> choices, I provide both patches here.

Thanks for the suggestions!  I went with the second one.  Could you 
please check that the changeset I've pushed to the public repo does what 
you want?